Problem 26.12

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The animation shows a spherical conductor surrounded by a conducting spherical shell.  The two conductors have equal but opposite charge and the voltage difference between the two is 50 V (position is given in centimeters and charge is given in nanocoulombs).  The field vectors for the electric field (kQ/r²) are shown in the region between the shell and the inner sphere and are zero everywhere else.  Restart.

1. Develop an expression for the charge as a function of the radius of the outer sphere and verify it with the animation.
2. Develop an expression for the capacitance as a function of radius. 
3. Does the capacitance increase or decrease with increasing shell size?  Explain.

Problem authored by Anne J. Cox.
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